A Danish inventor charged with murdering Swedish journalist Kim Wall in his home-made submarine had video footage on his computer showing women being violently killed, a court heard on Tuesday.

A police prosecutor said officers found images “which we presume to be real” of women being strangled and decapitated on the hard drive on Peter Madsen’s computer in a laboratory he ran.

That, together with new post-mortem evidence showing Wall was stabbed in her ribcage and genitals 15 times “around or shortly after her death,” was adding to the case against Madsen, the prosecutor, Jakob Buch-Jepsen, told the Copenhagen court.

DNA tests from Madsen’s nails, face and neck showed a clear match with Wall’s, Buch-Jepsen said, though the exact cause of death remained unknown. “Our suspicion hasn’t changed, it has been strengthened since (the last hearing on) September 5,” he added.

Madsen, who denies murdering Wall and another charge of mutilating her body, appeared in court via video link dressed in a green boilersuit.

He said the computer searched by police was not his. “They are the space laboratory’s tools which have been used by everyone in the laboratory,” he said. The court heard he had been working on building a space rocket in the lab.

Scanpix Denmark / Reuters
Peter Madsen has claimed Wall died accidentally after she hit her head on a hatch cover on his submarine

He remained calm during the pre-trial session, sitting with his hands folded most of the time. The court ordered him to be detained for another four months as investigations continue.